Adolescent girls who sleep late at night are more prone to weight gain than peers who sleep early, reveals a study published in JAMA Pediatrics (September). The study, conducted by Kaiser Permanente, a leading US-based healthcare company, evaluated the sleeping habits of 804 adolescents (418 girls and 386 boys) between the ages 11-16 who were asked to answer a set of questionnaires and wore an actigraph, a wristband to track physical activity.

Researchers also calculated their social jet lag — the difference between children’s weeknight and weekend bedtimes. Those who stay up later on weekends than weeknights experience high social jet lag, and are more likely to gain weight. The researchers found that teenage girls who stayed up late recorded an average 0.58 cm increase in waist size and 0.16 kilogram per square metre in body fat.

The study concluded that improving sleep schedules can prevent childhood and adolescent obesity, especially in girl children.